Ammonia production by the Haber-Bosch process is well known in the art. The process generally involves the production of a synthesis gas in a synthesis gas train and subsequent conversion of the synthesis gas to ammonia in a continuous synthesis loop. In the synthesis gas train, a hydrocarbon feedstock is desulfurized, reformed using steam and air, and suitably purified to produce a synthesis makeup gas comprising nitrogen and hydrogen at approximately stoichiometric proportions at a pressure between 2 and 7.6 MPa. In the synthesis loop, a portion of the synthesis gas is reacted over a suitable catalyst, typically iron-based, in an ammonia converter. Ammonia is separated from the unreacted (recycle) gas and makeup gas is added for return to the synthesis loop except for a small portion which is typically removed as a purge stream to control the concentration of inert components. Prior to reaction, the recycle gas is recompressed to the pressure of the ammonia synthesis loop, generally between 10 and 22.0 MPa depending on the particular process, and preheated.
Ammonia is generally recovered from the unreacted gas by condensation in an ammonia recovery loop. Hot reaction effluent is cooled in stages, first against boiler feed water for heat recovery in steam generation and reactor feed preheat units, followed by additional water cooling and chilling against an ammonia refrigerant to a temperature less than 0.degree. C. The recovery loop generally includes a low pressure ammonia refrigeration system made up of a multistage ammonia compressor and a water cooled condenser as is well known in the art. Following condensation, the ammonia condensate product is typically let-down to the pressure of the ammonia refrigeration system to flash out dissolved inert gases. A depressurized ammonia condensate is then removed as product for storage or other use.